(1) Field of the Invention
This invention relates to an improved machinery control device. More particularly this invention relates to machinery where a movable member is utilized to control itself or mechanisms that make up the machinery. Still more particularly, this invention relates to a magnetically actuated control device wherein an actuator for a responder permits free operation of the device as well as operation in confined quarters.
(2) Description of the Prior Art
Electrically controlled machines such as machine tools, assembly and forming machines, hoists, and a large variety of mechanical devices, commonly use "limit" switches to sense the position of a movable element and provide the necessary control. The control may be provided through the operation of a valve, a solenoid or relay, or the direct control of the machinery itself. In most applications a responder is mounted on the machine or apparatus for which the control is being provided, and an actuator is positioned adjacent the responder for selective operation of the responder. Ordinarily, the actuator is mounted on the movable component of the machinery, and the responder remains relatively stationary. The responder is actuated, for control purposes, as the actuator draws near the responder.
In complex electrically controlled machinery, such as automatic or semiautomatic equipment, a large number of actuators and responders may be required. In such installations, it is not desirable to mount a large number of switches upon the apparatus with the actuators or responders in exposed locations due to the likelihood of accidental damage to either or both switch elements.
Limit switches of various types are known, such as the mechanically actuated switch shown in U.S. Pat. No. 3,192,349. Mechanically actuated switches, due to the contact between the actuator and the responder necessary for operation, are unsuitable in certain applications. Magnetically actuated switches are known in the art, such as disclosed in U.S. Pat. No. 3,172,976, assigned to the assignee of the present invention. Magnetically actuated switches have the advantage of being actuable without requiring physical contact between the actuator and the responder.
If the switches known in the prior art must be used where space is an important consideration, difficulties arise. When machinery includes a reciprocating member which must pass through a sliding seal, as in a hydraulic power piston, actuators of the prior art must often be mounted on an extension affixed to the reciprocating member. Mounting of this nature is often required if control of functions corresponding to extended linear positions of the reaprocating member is desired. Often, the actuators and responders, of necessity, must be mounted at some distance from the main portion of the device, perhaps on an extension of a piston rod. To achieve operating stability, an outboard bearing for the piston rod extension is often required. An outboard bearing requires valuable, useful space and is vulnerable to contamination and abuse due to its separation from the main body of the machinery.